GB2161915A

GB2161915A - Liquid fuel burner

Info

Publication number: GB2161915A
Application number: GB08418529A
Authority: GB
Inventors: Prem Nath Bhambi; Harish Kumar Madan; Kuldeep Narain Dobhal; Valentin Leonidovich Gudzjuk
Original assignee: Council of Scientific and Industrial Research CSIR
Current assignee: Council of Scientific and Industrial Research CSIR
Priority date: 1984-07-20
Filing date: 1984-07-20
Publication date: 1986-01-22
Also published as: GB8418529D0; GB2161915B

Abstract

There is disclosed an atomising liquid fuel burner comprising a fuel pipe 3 with a fuel metering nozzle 5 at its outlet end, and primary and secondary air pipes 7, 10 with air impinging cones 9, 12 at their outlet ends. The fuel pipe 3 coaxially surrounds an inner primary air pipe 1 (or a solid cylindrical stem or rod), and another primary air pipe 7 coaxially surrounds the fuel pipe, a portion of the inner primary air pipe (or the solid stem or rod) protruding beyond the fuel metering nozzle by a length 6. <IMAGE>

Description

SPECIFICATION Film burner This invention relates to improvements in a liquid-fuel fired burner in which the fuel is atomised by air. Better atomisation is brought about by improved distribution of droplets in combustion air streams.

In the presently available air atomising oil burners (hereafter referred to as conventional burners) the atomising air or stream is made to impinge upon a solid stream of liquid fuel and the latter gets atomised due to momentum transfer between the atomising agent and the fuel resulting in coarse droplets of fuel which require more excess air and time to complete combustion.

The object of this invention is to propose a burner in which atomisation will be such that to complete combustion a lesser amount of excess air will be required resulting in fuel conservation, lower corrosion rate, higher turn down ratio and reduction in pollution. We have found that by: 1. passing an air stream through a hollow cylinder of liquid the thickness of the liquid wall of the fuel reduces to a fine film.

2. passing an air stream over a hollow cylinder of fuel the thickness of the hollow cylinder of liquid reduces to that of a fine film.

3. impinging an air stream on a hollow cylinder having thin liquid walls, the latter disintegrates into fine droplets.

The film burner of this invention consists of three coaxial cylindrical bodies; the innermost being a solid cylinder or a pipe, said solid cylinder or pipe being longer than the middle tube and the outermost tube ending in a cone.

The liquid fuel is fed through an annular space between the innermost tube or solid cylindrical body and the middle tube and the air is passed through the annular space between the middle and outermost tube and the innermost tube if used. The burner is lighted by applying a flame at its mouth.

The invention is described below with reference to the accompanying drawings illustrating one embodiment of this invention. In the drawings: Figure 1 is a sectional elevation of an embodiment of a burner according to this invention; Figure 2 is a sectional elevation of a conventional air atomising burner; Figure 3 is a sectional elevation of a lighter carrying a flame; and Figure 4 is a line diagram of the burner of Fig. 1 installed on a typical furnace.

Referring to Fig. 1 of the drawings the burner, also referred to as the film burner, of this invention consists of an inner primary air pipe 1 with a primary air regulating valve 2 at the inlet end, an oil pipe 3 with an oil regulating valve 4 at its inlet end and an oil metering nozzle 5 at the other end. The oil pipe is provided coaxially externally of the primary air pipe 1. The inner primary air pipe 1 protrudes out from the oil metering nozzle 5 by a length 6. An outer primary air pipe 7 with an outer primary air regulating valve 8 at its inlet has a primary air cone 9 at its free end and the pipe 7 is located coaxially around the oil pipe 3. A secondary air pipe 10 with a secondary air regulating valve 11 at its inlet has a secondary air cone 1 2 at its free end, the pipe 10 being located coaxially around the outer primary air pipe 7.

The conventional burner (Fig. 2) consists of a primary air pipe 1A having a primary air regulating valve 2A at one end and a primary air cone 2B at the other end; an oil pipe 3A with an oil regulating valve 4A at one end and an oil metering nozzle 5A located coaxially inside the primary air pipe 1A. The secondary air pipe 10A with the secondary air regulating valve 1 1A has its secondary air cone 12A located coaxially around the primary air pipe 1A.

In the burner of this invention (Fig. 1) oil 1 3 is fed into the oil pipe 3 by controlling the oil regulating valve 4. The oil 1 3 passes through the oil metering nozzle 5 in the form of an oil cylinder around protruding portion 6 of the inner primary air pipe 1. Outer primary air 14 enters into the outer primary air pipe 7 by operating the outer primary air regulating valve 8. Outer primary air 14 impinges upon the oil cylinder along the protruding length 6 thereby reducing considerably the thickness of the cyclinder formed by the oil. This oil cylinder leaves the free or open end 1 6A of the inner primary air pipe 1 in the form of a thin oil cyclinder. Inner primary air 1 5 is fed into inner primary air pipe 1 by regulating the inner primary air valve 2.Inner primary air 1 5 finally passes through the hollow oil cylinder leaving the end 1 6B of the outer primary air nozzle and together with primary air 14 reduces the thickness of the oil wall in the oil cylinder to a very fine oil film which cannot sustain itself and therefore disintegrates into fine oil droplets.

The mix of oil and primary air 1 5 and 14, in the form of fine droplets, passes out of the secondary air cone 1 2 (together with secondary air 17, if any) from the burner end 1 6 into the furnace 1 8 (Fig. 4), the burner being fitted by the secondary air cone 1 2 to the furnace mouth where a flame 1 9 (Fig. 3) is applied so that the stable flame of atomised oil is established.

Instead of inner primary air pipe 1, a solid stem or cylindrical rod, protruding as at 6, may be provided, the primary air being supplied by the outer pipe 7 only.

In case of the conventional burner (Fig. 2) oil 1 3 is passed through the oil pipe 3A by regulating the oil regulating valve 4A. The oil finally leaves the oil metering nozzle 5A in the form of a solid stream 13A. Primary air 1 5 is passed through the primary air pipe 1 A by regulating the primary air regulating valve 2A and then the primary air 1 5 is finally made to impinge upon the solid stream 1 3A of oil 1 3 outside the oil metering nozzle 5A, when the solid oil stream 1 3A breaks into droplets due to momentum transfer between the solid oil stream 1 3A and primary air 1 5. Thus atomised oil forms a combustible oil/air mixture which is fed inside the furnace where it is fired by a flame.

In the case of the burner of this invention the oil 1 3 leaves the burner end 1 6 in the form of a finely atomised oil-air spray whereas oil 1 3 in the case of the conventional burner (Fig. 2) leaves in the form of thick oil-air droplets.

The thin cylinder of oil in the burner of this invention (Fig. 1) forms finer droplets of more uniform size than those formed by the impingement of air on the thick stream of oil in the case of the conventional burner (Fig. 2). Thus air and fuel in the case of the burner of this invention (Fig. 1) get mixed more thoroughly and form a more uniform oil-air mixture resulting in complete combustion with a lesser amount of excess of air and over a larger turns down ratio.

The film burner of this invention can be designed for any capacity and the material used in the construction of various parts as shown in Fig. 1 can be of mild steel, stainless steel, cast, cast iron, brass, etc., depending upon the composition of the fuel oil used.

The burner of this invention gave the following performance in comparison to the conventional burner of the same size: Performance Conventional Burner Film Burner 1. Capacity kg/hr. Max. 60 65 2. Turn down ratio achieved. 1:3.5 1:7 3. Excess air % 25-30 5 4. Primary air pressure mm W.G. 750 400 5. Saving in fuel over conventional kg/hr - 1 6. Saving in power over conventional burner % - 60% The burner of this invention has the following advantages over the conventional burners: 1. It requires lesser excess air for complete combustion.

2. Due to less excess air requirement, fuel saving to do the same amount of heating is of the order of 2%.

3. Due to lower excess air requirement the corrosion tendency of products of combustion is absent.

4. Requirement of lower air pressure leads to power saving up to 60%.

It will be appreciated that it is not intended to limit the invention to the above example only, many variations, such as might readily occur to one skilled in the art, being possible, without departing from the scope thereof as defined by the appended claims.

For example, one or more swirlers may be provided in the fuel pipe of the air pipes.

Claims

1. An air/stream atomising liquid fuel burner comprising a fuel pipe with fuel metering nozzle at outlet end, primary and secondary air pipes with air impinging cones at outlet ends wherein the fuel pipe coaxially surrounds an inner primary air pipe or a solid cylindrical stem or rod and another primary air pipe coaxially surrounds the fuel pipe, a portion of the inner primary air pipe or the solid stem or rod protruding beyond the fuel metering nozzle.

2. A burner as claimed in claim 1 wherein swirler(s) is (are) provided in the fuel pipe.

3. A burner as claimed in claim 2 wherein swirlers are provided in the air pipes.

4. An air/stream atomising liquid fuel burner substantially as described herein with reference to and as illustrated by the Fig. 1 of the accompanying drawings.